CZ283753B6 - Method of monitoring operation of a recirculating control system and apparatus for making the same - Google Patents

Abstract

According to the method of monitoring the performance of the recirculation control system, the fluid is directed through a recirculation control system including a main inlet (12) to maintain a minimum flow, a main outlet (14) and a recirculation outlet (16) and a piston (26) with a piston chamber (24) for controlling the fluid flow through the recirculation outlet (16). Data is obtained on the fluid pressure flowing through the main inlet (12), fluid pressure data flowing through the main outlet (14), fluid pressure data in the piston chamber (24), and processed to analyze the recirculation system. The method for carrying out the method comprises a main inlet (12), a main outlet (14) and a recirculation outlet (16), means for obtaining fluid pressure data flowing through the main inlet (12), means for obtaining fluid pressure data flowing through the main outlet (14) ) and means for obtaining fluid pressure data flowing through the system and directed to the recirculation output (16), and an analyzer for analyzing the data obtained

Description

(57)

A method of monitoring the operation of a recirculating control system according to which a liquid is rectified by a recirculating control system comprising a main inlet (12). Maintaining a minimum flow rate, the main outlet (14) and the recirculation outlet (16), and the piston (26) with the piston chamber (24) for regulating the fluid flow through the recirculation outlet (16), obtaining fluid pressure data flowing through the main inlet ( 12), the fluid pressure data flowing through the main outlet (14), the fluid pressure data in the piston chamber (24), and processed for analyzing the operation of the recirculation system. The apparatus for carrying out the method comprises a main inlet (12), a main outlet (14) and a recirculation outlet (16), further means for obtaining liquid pressure data flowing through the main inlet (12), means for acquiring liquid pressure data flowing through the main outlet (14), and means for acquiring fluid pressure data flowing through the system and routed to the recirculating outlet (16), and an analyzer for analyzing the data obtained to determine system operation.

A method for monitoring the operation of a recirculating control system and apparatus for performing the method

Technical field

The invention relates to control systems or valves, and in particular to a method and apparatus for monitoring the operation of recirculating control systems or valves.

BACKGROUND OF THE INVENTION

A recirculation control system is often used with centrifugal pumps to prevent the pump from overheating. Overheating is avoided by maintaining a constant minimum flow through the pump. In times of low demand for pump fluid recirculation, the recirculation control system automatically recirculates sufficient fluid from the pump outlet to maintain at least a minimum flow through the pump. The recirculated fluid is then returned to the tank. The recirculation control system may comprise a combination of different valves or one recirculation control valve. A valve of this type is described in U.S. Pat. No. 4,967,783 and is completely separate and includes a flow sensor, a bypass control valve, and a multi-stage pressure relief valve, all housed in a single body. Other recirculating control valves are described in U.S. Pat. Nos. 4,779,639 and 4,942,502.

A disadvantage of the recirculation control system or the ventilator is that the operator of the equipment can find it very difficult to verify their correct operation. Often unnecessary dismantling of equipment and inspection of certain components are performed. However, even disassembly cannot verify that the valve is operating correctly under all operating conditions. In addition, inspection and repair of the valve is usually performed by qualified personnel. This brings additional costs and planning problems.

Permanently correct operation of the recirculation systems is crucial for the protection of the pump. It is therefore an object of the present invention to monitor the operation of a valve during its operation.

Another object of the invention is to allow remote monitoring of the recirculation control valves. Another object of the invention is to provide an indicator of valve operation. It is also an object of the invention to allow continuous monitoring of the valve.

SUMMARY OF THE INVENTION

The aforementioned drawbacks are largely overcome by a method and apparatus for monitoring and analyzing the operation of the recirculation control system of the invention. According to the invention, the pressure of the liquid flowing through the control system is measured directly by the pressure and differential pressure transducers in the main inlet, the main outlet and the recirculation path of the control system. When the means for controlling the flow of fluid to the recirculation outlet comprises a piston with a piston chamber, the pressure in the recirculation path is determined by measuring the pressure in the piston chamber. Pressure data is transmitted to the analyzer to detect valve operation.

The invention includes a method of monitoring the operation of a recirculating control system to which liquid is directed, the control system having a main inlet, a main outlet, and a recirculation outlet. According to the method of the present invention, the pressure of the liquid flowing through the system at the main inlet of the system is obtained, the pressure of the liquid flowing through the system at the main outlet of the system is obtained, and the pressure of the liquid flowing through the recirculation path of the system is obtained. If the recirculation control system comprises a means for controlling the flow of liquid to the recirculation outlet that includes a piston with a piston chamber, the pressure is determined during operation of the system

In the recirculation path by measurement in the piston chamber. The pressure data obtained is analyzed to detect valve operation.

The invention also includes a device for monitoring and analyzing the operation of the recirculation control system. The apparatus comprises means for acquiring fluid pressure data flowing through the system at the main system entry, means for acquiring fluid pressure data flowing through the system at the main system exit, and means for acquiring fluid pressure data flowing through the system recirculation path. If the recirculation control system comprises means for regulating the flow of fluid to the recirculation outlet that includes a piston with a piston chamber, the device acquires a fluid pressure flowing through the recirculation path in the piston chamber during operation of the assembly. The pressure data obtained is analyzed to detect valve operation.

Overview of the drawings

The invention will be explained in more detail with reference to the accompanying drawing. In order to illustrate the invention, a preferred embodiment thereof is shown in the drawing, but of course it is believed that the invention is not limited to the particular arrangement and equipment. Fig. 1 is a schematic cross-sectional view of a recirculation valve according to a preferred embodiment; Fig. 2 is a cross-sectional view taken along line 2-2 of Fig. 1 showing the recirculation outlet and pressure sensor position; Fig. 4 is a graphical representation of the valve pressure during operation; and Fig. 5 is a flowchart showing a logic operation sequence for analyzing the valve pressure record of Fig. 1.

DETAILED DESCRIPTION OF THE INVENTION

The method of the invention comprises monitoring critical parameters of the operation of the recirculation control system during its operation. These parameters are the fluid pressure flowing through the main inlet of the system, the fluid pressure flowing through the main outlet of the system, or the difference between the inlet and outlet pressure, and the fluid pressure flowing through the recirculation outlet of the system. When the recirculation control valve comprises a control valve and a piston device for regulating the flow of fluid through the recirculation outlet, as disclosed in US 4,967,783, it is preferable to measure and monitor the pressure of the fluid in the piston chamber rather than in the recirculation outlet. The fluid pressure data is preferably collected directly by a pressure and differential pressure transducer and transmitted to an analytical device where the data is analyzed to recognize valve operation.

1 and 2 show a recirculation control valve monitoring device according to the invention. The recirculation control valve 10 comprises a main body 11 with a main inlet 12 and a main outlet 14. The main inlet 12 is connected to the first control valve 17 via a recirculation channel 20.

The recirculation channel 20 communicates with the housing 22 in which the piston 26 is slidably mounted to the other side with the recirculation outlet 16 via the aperture 15. When withdrawal from the pump is required, which corresponds to a drop in outlet pressure in the main outlet 14. actuates a second control valve 28 by means of which the piston chamber 24 is filled with liquid. As the piston chamber 24 is filled with liquid, the sliding piston 26 is pushed upwardly toward the stop on the housing 22, thereby regulating the flow of liquid to the recirculation outlet 16.

The pressure transducer 30 senses the fluid pressure in the main inlet 12 through the orifice 31 and converts and transmits this data in the form of an electronic signal. Similarly, the pressure transducer 36 senses the fluid pressure in the piston chamber 24 through the aperture 37. The differential pressure transducer 32 measures the difference between the pressures.

The liquid 1151HP and 1151DP, commercially available from Rosemount, Inc., Eden Prairie, Missouri, may be used as a suitable pressure transducer or differential pressure transducer.

Referring to FIG. 3, a recirculation control system and monitoring device including the recirculation control valve of FIGS. 1 and 2 is shown. Liquid from the pump 40 enters the recirculation control valve 10 through the main inlet 12 and exits through the main outlet 14 as required by the user. It will be appreciated that the function of the recirculation control valve 10 is to maintain at least a minimum flow through the pump 40 to prevent it from overheating. When the user's demand 42 for pump fluid drops below the minimum flow rate through the pump 40, the recirculation control valve 10 directs the liquid flow to the recirculation outlet 16 in addition to the current flowing through the main outlet 14. Sufficient liquid is diverted to the recirculation outlet 16 so that inlets 14 and 16 equals at least the minimum flow rate required for pump 40. In this way, the flow rate through inlet 12 and thus the pump 40 can always be maintained above the minimum flow rate by directing additional flow to the recirculation outlet 16. Inlet pressure transducer 30, differential the pressure transducer 32 and the pressure transducer 36 transmit the respective data through suitable conductors 44, 46 and 48, shown in dashed lines, to the recirculation valve operation analyzer 50. The analyzer 50 receives and analyzes the transmitted pressure data and indicates the operation of the valve.

The curves plotted in the pressure-flow coordinates of FIG. 4 illustrate the characteristics of the control recirculation valve 10 in the preferred embodiment of FIGS. 1 and 2. The curves represent the predicted fluid pressure readings as a function of flow through the main outlet 14. The horizontal axis 52 represents the main the flow rate through the main outlet 14 in gallons per minute (rpm) and is referred to herein as the "main flow". The vertical axes 54 and 55 represent the liquid pressure in pounds per square inch (kPa).

The inlet pressure curve 56 represents the liquid pressure in the main inlet 12 as a function of the main flow through the main outlet 14, transmitted by the inlet pressure transducer 30. The piston pressure curve 58 represents the liquid pressure in the piston chamber 24 as a function of the main flow transmitted by the piston pressure transducer 36. Similarly, the differential pressure curve 60 represents the pressure difference between the main inlet 12 and the recirculating outlet 16 as a function of the main flow through the main outlet 14 transmitted by the differential pressure transducer 32. The curve 57 represents the stroke of the disc 21 inside the valve 10 and is shown for comparison only. The curve 59 represents the bypass of the valve 10 as a function of the main flow and is also shown for comparison only.

According to an explanatory example, the recirculation valve of the invention is designed to begin to divert fluid through the recirculation outlet 16 when the main flow through the main outlet 14 drops below 500 gpm (1890 rpm) as shown in point 61.

From 500 gpm (1890 rpm), a vertically dashed line 62 intersects all three pressure curves to indicate predicted pressure values at the indicated locations at a flow rate of 500 gpm (1890 rpm) below which recirculation is required. Above 500 gpm (1890 rpm) no recirculation is required. The dashed line 62 intersects the differential pressure curve 60 at point 64, which corresponds to 5 psi (34.5 kPa) and is referred to as the differential pressure setpoint. Any differential pressure value equal to or greater than 5 psi (34.5 kPa) of the differential pressure setpoint indicates that the main flow through main outlet 14 is at least equal to or greater than the required minimum flow rate of 500 gpm (1890 rpm) ) and hence no recirculation is required by the recirculation output 16.

Comparing the inlet pressure curve 56 and the piston pressure curve 58, it is clear that whenever the main flow is the main outlet 14 at a minimum flow rate of 500 gpm (1890 rpm) or higher (curves 56 and 58 shown to the right of the dashed line 62) , the piston pressure curve 58 is

-3E 283753 B6 substantially identical to the inlet pressure curve 56. However, when the main flow drops below the minimum flow rate of 500 gpm (18901 / min), (to the left of the dashed line 62), the piston pressure curve 58 drops to less than half the value of the inlet pressure curve 56. This drastic change in piston pressure is a direct result of the flow being introduced into the recirculating outlet 16 when the main flow falls below the minimum flow rate.

These curves can be used to analyze the operation of the recirculation control valve 10. First, the state of the main flow through the main outlet 14 is determined. Whenever the differential pressure is greater than the value at the differential pressure setting point 64 (5 psi (34.5 kPa) according to the example) , the main flow rate through the main outlet 14 is higher than the required minimum flow rate and hence no recirculation is required. This condition is referred to as high flow. Likewise, whenever the differential pressure value is lower than the value at the differential pressure setting point 64, the main flow rate is less than the required minimum flow rate and it is necessary to recirculate through the recirculation outlet 16. This condition is referred to as low flow. When the flow status of the main outlet 14 is known, the actual operation of the control valve 10 is detected. When the main flow condition of the main outlet 14 is high (no recirculation is required), the piston pressure should be substantially equal to the inlet pressure as shown by curves 56 and 58 to the right of the dashed line 62. When the piston pressure is lower than the inlet pressure, this is probably because the fluid leaks through the control valve control valve 10 and the recirculation outlet 16. When the flow condition is high and the piston pressure is substantially half or less than half the inlet pressure, the recirculation bypass valve is opened. Similarly, when the flow condition is low (recirculation required), the pressure in the piston chamber should be half the inlet pressure or less, as shown by curves 56 and 58 to the left of the dashed line 62. When the piston pressure is not so low, due to the closed error, no fluid is recirculated and the minimum required flow rate through the pump 40 is not maintained.

Obviously, the curves shown in FIG. 4 are for illustrative purposes only. Each recirculation valve of the preferred embodiment will have its specific value at the differential pressure setting point 64 depending on the valve type and the required minimum flow rate for the pump to be protected.

Referring now to Figures 3 and 5, the analyzer 50 will now be described. Those skilled in the art will recognize that there are many ways to transmit pressure data, including electrical analog signals, electrical digital signals, as well as transmission media such as conductors, optical fibers, or radio signals. The transfer method used in the present invention is analog wire transfer. The analyzer 50 comprises an indicator light panel 70 comprising light indicators 94, 96, 98, 100, and 102, and an internal, not shown, electrical circuit that analyzes pressure data according to a programmed logic operation as shown in Figure 5, which will be described.

Fig. 5 shows a conventional block diagram. Individual rhombic blocks represent logical operations, such as comparing data, and rectangular blocks represent a step in a sequence of individual steps, such as illuminating a light indicator.

The logic operation begins with the input of all three pressure readings to the inlet block 72. At this point, in the decision block 74 it is decided whether the main flow through the valve 10 and the outlet 14 is high or low. The decision is made by comparing the differential pressure reading to a preset differential pressure setpoint value. If the differential pressure is lower, the flowchart continues to block 76. If the differential pressure is higher, the flowchart continues to block 84. For now, suppose the differential pressure is lower and the flowchart continues to block 76. Block 76 lights up on the light panel 70 a low main flow light indicator 94 to indicate that recirculation is required by the recirculation outlet 16 to maintain a minimum flow. In decision block 78, the piston pressure is compared to half

Of the inlet pressure. If the piston pressure is less than half the inlet pressure, the flowchart continues to block 80, with the open bypass light indicator 96 illuminated on the light panel 70, indicating that the recirculation valve is operating properly. However, if, instead, the piston pressure is not less than half the inlet pressure, the flowchart continues to block 82, with a light indicator 102 illuminating on the light panel 70 indicating that the bypass is closed due to an error and that the recirculation valve does not properly recirculate the liquid.

Upon returning to block 74, high pressure is now assumed and the flowchart continues to block 84. Block 84 lights the indicator light 100 to indicate that the main flow is high (no recirculation is required). The flowchart continues to blocks 86 and 90. In decision block 86, it is determined whether the piston pressure is less than the inlet pressure. If the outcome of the decision is positive, the flowchart continues to block 88, illuminating the indicator light 98 indicating leakage of the control valve. If the decision result in block 86 is not positive, this part of the flowchart ends.

Upon returning to block 90, it is decided whether the piston pressure value is less than half the inlet pressure value. If the outcome of the decision is positive, the flowchart continues to block 92 while the indicator light 96 is lit to indicate that the bypass is open. An illuminated indicator light 96 in combination with an illuminated indicator light 100 indicates a serious valve problem.

This logical operation was found to be continuous. As these three pressure values are continuously monitored and analyzed, the logic operation is repeated continuously. When the values change, the indicator lights also change. The electrical circuits of the preferred embodiment for performing said logic operation acquire data as analog signals from converters 30, 32 and 36. The signals are then converted to digital signals and processed in combinational logic circuits to achieve the desired output or indication. Those skilled in the art will readily understand how to construct such a device, as well as alternative ways of performing a logical operation, including loading data into a programmable microprocessor. Alternative methods and devices for indicating or displaying the results of a logical operation are also well known and include displaying these results on a monitor. The analyzer 50 may be located at the location of the control valve 10 or at a remote location. In addition to the analyzer 50, a remote analyzer 104 can be used to obtain the necessary signals using the conductors 106 shown in dashed lines. Appropriate labels may also be added to the light panel 70 for each light indicator.

It will be apparent to those skilled in the art that the disclosed embodiment may be altered without departing from the scope of the inventive concept. It is therefore to be understood that this invention is not limited to the particular embodiment disclosed, but covers all modifications that are included within the scope of the invention as defined in the claims.

Claims (7)

PATENT CLAIMS A method of monitoring the operation of a recirculation control system, comprising the steps of channeling fluid through a recirculation control system, comprising a main inlet (12) maintaining a minimum flow rate, a main outlet (14), a recirculation outlet (16) and a piston (26) in the piston chamber. 24) for controlling the fluid flow through the recirculating outlet (16), characterized in that the fluid pressure data flowing through the main inlet (12), the fluid pressure data flowing through the main outlet (14), the fluid pressure in the piston chamber are obtained (24), and these data will be used to analyze the operation of the recirculation system. - 5 GB 283753 B6 Method according to claim 1, characterized in that the fluid pressure data passing through the main outlet (14) is obtained in the form of a pressure difference between the fluid pressure in the main inlet (12) and in the main outlet (14). The method of claim 1, wherein the step of utilizing the obtained data comprises the steps of calculating a pressure difference between the obtained liquid pressure passing through the main inlet (12) and the obtained liquid pressure passing through the main outlet (14), and comparing the calculated pressure difference with a predetermined pressure difference setpoint value, comparing the obtained pressure in the piston chamber (24) with the obtained inlet pressure and using the result of comparing the pressure difference with a predetermined pressure difference setting point and comparing the pressure in the piston chamber (24) with the inlet pressure k system activity detection. Method according to claim 2, characterized in that the step of using the obtained data comprises the steps of comparing the gained differential pressure with a predetermined value of the setpoint of the differential pressure, comparing the obtained pressure in the piston chamber (24) with the obtained inlet pressure. system activity detection. A device for monitoring the operation of a recirculation control system, comprising a main inlet (12) to maintain a minimum flow rate, a main outlet (14), a recirculation outlet (16), a piston (26) in the piston chamber (24) for controlling fluid flow to the a recirculation outlet (16) characterized by. comprising means for acquiring fluid pressure data flowing through the main inlet (12), means for acquiring fluid pressure data flowing through the main outlet (14), and means for acquiring fluid pressure data in the piston chamber (24), means for analyzing obtained data to determine the operation of the system. Device according to claim 5, characterized in that the obtained fluid pressure data flowing through the main outlet (14) forms a pressure differential pressure between the fluid pressure in the main inlet (12) and in the main outlet (14). Device according to claim 5 or 6, characterized in that the means for analyzing the obtained data comprises a logical operating device.